[Detnet] Finetuning End.R description in draft-ietf-spring-sr-redundancy-protection

[Balázs Varga A <[e-mail]>]

Hi,

the draft's technical content seems to be quite stable.
Feedback from the WG on one possible improvement would be
highly appreciated.

In order to make the draft's text similar to RFC8986
format the following changes proposed in section 4.1.
"Redundancy Segment Endpoint Behavior":

--- OLD TEXT
   S01. When an SRH is processed {
   S02.   If (Segments Left != 0) {
   S03.    Send an ICMP Parameter Problem message to the Source Address
                with Code 0 (Erroneous header field encountered),
                and Pointer set to the Segments Left field,
                interrupt packet processing and discard the packet
   S04.   }
   S05.   Extract the ARG part of the SID
   S06.   Remove the outer IPv6 header with all its extension headers
   S07.   Forward the exposed payload and the ARG part to the Redundancy
          functionality
   S08. }

--- NEW TEXT
   S01. When an SRH is processed {
   S02.   If (Segments Left != 0) {
   S03.    Send an ICMP Parameter Problem message to the Source Address
                with Code 0 (Erroneous header field encountered),
                and Pointer set to the Segments Left field,
                interrupt packet processing and discard the packet
   S04.   }
   S05.   Proceed to process the next header in the packet
   S06. }

When processing the Upper-Layer header of a packet matching a FIB entry
locally instantiated as an End.R SID, N does the following:

   S01. If (Upper-Layer header type == ( 4(IPv4) OR 41(IPv6) OR 143(Ethernet) ) {
   S02.   Extract the ARG part of the SID
   S03.   Remove the outer IPv6 header with all its extension headers
   S04.   Forward the exposed payload, type and the ARG part to the Redundancy
          functionality
   S05. } Else {
   S06.    Process as per Section 4.1.1 of RFC8986
   S07. }

--- END OF CHANGE

The change would address the followings:
- similar format used for the definition of the End.R behavior as the format used in RFC8986
- more clear description of the processing of the Upper-Layer header

Any comments are welcome.

Thanks & Cheers
Bala'zs

Ps: this draft impacts DetNet WG as well on using an SRv6 data plane for DetNet,
so the DetNet list also cc-ed.